Communication devices such as terminals are also known as e.g. User Equipments (UE), mobile terminals, stations (STAs), wireless devices, wireless terminals and/or mobile stations. Communications devices are enabled to communicate wirelessly in a wireless communications network, such as a Wireless Local Area Network (WLAN), or a cellular communications network sometimes also referred to as a cellular radio system or cellular networks. The communication may be performed e.g. between two communications devices, between a communications device and a regular telephone and/or between a communications device and a server via an Access Point (AP) operating in an access network and possibly one or more core networks, comprised within the wireless communications network.
The above communications devices may further be referred to as mobile telephones, cellular telephones, laptops, or tablets with wireless capability, just to mention some further examples. The communications devices in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the access network, such as a Radio Access Network (RAN), with another entity, such as another communications device or a server.
The communications network covers a geographical area which is divided into geographical subareas, such as coverage areas, cells or clusters. In a cellular communications network each cell area is served by an AP such as a base station, e.g. a Radio Base Station (RBS), which sometimes may be referred to as e.g. “eNB”, “eNodeB”, “NodeB”, “B node”, or Base Transceiver Station (BTS), depending on the technology and terminology used. The base stations may be of different classes such as e.g. macro eNodeB, home eNodeB, micro eNode B or pico base station, based on transmission power, functional capabilities and thereby also cell size. A cell is the geographical area where radio coverage is provided by the base station at a base station site. One base station, situated on the base station site, may serve one or several cells. Further, each base station may support one or several communication technologies. The base stations communicate over the air interface operating on radio frequencies with the communications devices within range of the base stations. In the context of this disclosure, the expression Downlink (DL) is used for the transmission path from the base station to the communication device. The expression Uplink (UL) is used for the transmission path in the opposite direction i.e. from the communications device to the base station.
In 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE), base stations, which may be referred to as eNodeBs or even eNBs, may be directly connected to one or more core networks.
3GPP LTE radio access standard has been written in order to support high bitrates and low latency both for uplink and downlink traffic. All data transmission is in LTE controlled by the radio base station.
Institute of Electrical and Electronics Engineers (IEEE) 802.11 is a set of Media Access Control (MAC) and PHYsical layer (PHY) specifications for implementing Wireless Local Area Network (WLAN) computer communication in the 2.4, 3.6, 5, and 60 GHz frequency bands. They are created and maintained by the IEEE Local Area Network (LAN)/Metropolitan Area Network (MAN) Standards Committee (IEEE 802). The base version of the standard was released in 1997, and has had subsequent amendments. The standard and amendments provide a local area wireless computer networking technology that allows electronic devices to connect to a network. A WLAN is sometimes referred to as a WiFi network.
Recently, there has been rise in the use of different radio technologies, such as WLAN technology according to the IEEE 802.11 and the 3GPP LTE radio access technology, to provide a distribution medium for device to device communication between communications devices within the proximity of each other.
Wireless connectivity may be provided over so-called social channels. By the expression “social channels” when used in this disclosure is meant communications channels enabling communication among people sharing similar interests e.g. interested in selling or buying specific services, interested in common hobbies etc. For instance, the Wi-Fi Alliance has been working on the so called Wi-Fi Direct and Neighbour Awareness Networking (NAN), both of which enables Device-to-Device (D2D) communication between communications devices. The NAN is sometimes also referred to as Wi-Fi Aware. In such a setting, communications devices may scan the social channels to discover other communications devices such as other wireless devices or wireless Access Points (APs). The NAN enables power efficient discovery of nearby information, such as information relating to communications devices, people, and access points, and of nearby services, by means of D2D communication. The NAN will make it easy for a user to find services available in the area that match preferences set by the user, and it is optimized to work well even in crowded environments. More details is be found at http://www.wi-fi.org/discover-wi-fi/wi-fi-aware and https://www.wi-fi.org/wi-fi-nan-technical-specification-v10 (Section 1 and 2 covers Introduction and Architecture of NAN).
A communications device capable of NAN is sometimes herein referred to as a NAN communications device or a NAN device. The NAN device may be defined as a mobile handset and/or laptop or any other communication device certified by the Wi-Fi Alliance Wi-Fi Aware program. The communication between several NAN devices is based on the IEEE 802.11n physical layer which operates at 2.4 GHz and 5 GHz carrier frequencies. The NAN is defined with a new MAC mechanisms to support a formation of a cluster, such as a cluster formation, to support master selection within a cluster, cluster discovery and acquiring synchronization within a cluster, cluster selection and merging, NAN service discovery protocol etc. The NAN protocol supports the formation of the cluster and the maintaining of a time synchronization within the cluster based on transmissions of one or more NAN synchronization beacons.
FIG. 1 schematically illustrates a communications network according to the prior art. The communications network comprises a station (STA) acting as a NAN Master, e.g. a NAN STA Master, and four stations, e.g. stations STA1-STA4. The NAN master device, i.e. the NAN device acting as the master device within a cluster, transmits one or more NAN discovery beacons, cf. FIG. 2 which will be described below, to announce the existence of the cluster to one or more neighbour communications devices, e.g. to one or more of the stations STA1-STA4, which are not part of the cluster. A cluster comprising one or more NAN devices, e.g. a NAN master device and one or more NAN slave devices, may be referred to as a NAN cluster. Further, the one or more NAN devices within the cluster transmit one or more NAN service discovery frames to either publish or subscribe to one or more services within a cluster.
As also illustrated in FIG. 1, D2D communications between the different STAs STA1-STA4 is provided in the communications network.
FIG. 2 schematically illustrates the transmissions of NAN Discovery beacons from a NAN device, e.g. the NAN STA Master of FIG. 1, to announce the existence of a cluster. Further, FIG. 2 schematically illustrates the announcing of the synchronization timing and service discovery by means of the NAN Sync beacons and the NAN Service Discovery frames, respectively.
The NAN Discovery Beacon frame is a modified IEEE 802.11 Beacon management frame transmitted outside NAN Discovery Windows to facilitate discovery of NAN clusters. Each NAN device in a master role shall transmit the NAN Discovery Beacon frames.
Further, the NAN synchronization beacon is a modified IEEE 802.11 Beacon management frame transmitted inside NAN Discovery Windows used for NAN timing synchronization.
Furthermore, the NAN Service Discovery frames enable the NAN devices to look for services from other NAN devices and to make services discoverable for other NAN devices. More details may be found in the NAN Release 1 specification: https://www.wi-fi.org/downloads-registered/Neighbor_Awareness_Networking_Technical_Specification_v1_0_0.pdf/Neighbor%2BAwareness%2BNetworking%2BTechnical%2BSpecification%2Bv1.0/29731
The NAN service discovery frame is a public action frame and it utilizes the Vendor Specific Public Action frame formats defined in the IEEE specification with the Wi-Fi Alliance Organizationally Unique Identifier (OUI) and the Wi-Fi Alliance OUI type indicating the NAN operation. As mentioned above, the NAN device transmits NAN service discovery frames to either publish or subscribe to services within a cluster.
One or more NAN Information Elements are carried in one or more NAN discovery beacon frames. The NAN Information Element is a Vendor Specific Information Element with the Wi-Fi Alliance OUI and a Wi-Fi Alliance OUI type to indicate the NAN operation. The NAN master device transmits, to one or more neighbour communications devices which are not part of the cluster, one or more NAN discovery beacons to announce the existence of the cluster.
It is envisioned that future Wi-Fi technologies may also support data transfer capability along with the existing capability to publish and/or subscribe to the services. The new technologies may support concurrent operations with other Wi-Fi or 3GPP technologies.
The 3GPP Long Term Evolution (LTE) Release 12 includes D2D communication to enable communication between nearby communications devices. Communication based on proximity between communications devices is provided using a function referred to as Proximity Services (ProSe). The ProSe comprises two types of communications. Firstly, the ProSe comprises a direct communication between two communications devices. The direct communication is sometimes referred to as a direct mode communication. Secondly, the ProSe comprises a routed communication between two communications devices, wherein the communication is routed via the AP e.g. a base station. The routed communication is sometimes referred to as a routed mode communication or a locally routed mode communication since the AP, e.g. the base station, may be used as a relay. The ProSe is the services that may be provided by the 3GPP communications system when communications devices are located in proximity to each other. Thus, the ProSe provides the communications device, e.g. a user equipment (UE), with parameters to access the functionality, allocate and/or map application identifiers, store a reference point towards an application server, other ProSe Functions, home subscriber server (HSS) and UE. The 3GPP communications system enablers for ProSe comprise the following functions (see 3GPP TS 23.303 V13.0.0): Evolved Packet Core (EPC) level ProSe Discovery, EPC support for WLAN direct discovery and communication, Direct discovery, Direct communication, and UE-to-Network Relay.
The ProSe, see 3GPP TR 22.803 V12.2.0, assumes use cases, wherein an operator network controlled discovery and communication procedure takes place between communications devices that are located in proximity with each other, under continuous network control, and are under the 3GPP network coverage, for:
1. Commercial and/or social use
2. Network offloading
3. Public Safety
4. Integration of current infrastructure services, to assure the consistency of the user experience including reachability and mobility aspects.
Additionally, the use cases comprise:
5. Public Safety, in case of absence of the E-UTRAN coverage. This may be subject to regional regulation and operator policy, and limited to specific public-safety designated frequency bands and terminals.
Details on the ProSe, based on 3GPP TR 22.803 V12.2.0, will be described below.
Data Paths for the ProSe Communications
As currently specified, a default data path scenario is when two communications devices located in proximity, e.g. close proximity, with each other are communicating, and their data path, e.g. their user plane data path, goes via the operator's communications network. By the expression “close proximity” when used in this disclosure is meant that two communications devices are able to send and receive data, signals and/or beacons to and from each other. When the expression “close proximity” is used for ProSe it means that the two communications devices are within the same cellular cell coverage or within the same geographical neighbourhood. Further, when the expression “close proximity” is used for WLAN NAN it means that the communications devices are located within the range of the WLAN i.e. in the order of tens or hundreds of meter. The typical data path for ProSe communication is shown in FIG. 3, wherein the communication between a first communications device denoted UE1 and a second communications device denoted UE2 goes via a respective base station denoted eNB1 and eNB2, respectively, and via a Serving Gateway (SGW) or a Public Data Network (PDN) Gateway (PGW) of e.g. a core network.
In a ProSe communication scenario, when two communications devices are located in proximity with each other, they may be able to use a direct mode communications path or a locally-routed communications path.
For example, in a 3GPP LTE spectrum, the operator may move the data path, e.g. the user plane data path, off the access network and the core network onto one or more direct links between the communications devices. FIG. 4 schematically illustrates a direct mode data path in the communications network, e.g. in an Evolved Packet System (EPS), for communication between the first communications device UE1 and the second communications device UE2.
Another example is when the data path is locally-routed via one or more of the base stations, e.g. the first base station eNB1 and/or the second base station eNB2. FIG. 5 schematically illustrates a locally-routed mode data path in the communications network, e.g. the EPS, for communication between the first communications device UE1 and the second communications device UE2 when both communications devices UE1, UE2 are served by the first base station eNB1.
Control Paths for the ProSe Communication
For the ProSe Communication scenarios depicted in FIG. 4 and FIG. 5, several control path scenarios may apply. Examples of potential control paths for different situations will be described below with reference to FIGS. 6-8.
FIG. 6 schematically illustrates an example control path for network-supported ProSe communication between the first and second communications devices UE1, UE2 when being served by the same base station, e.g. the first base station eNB1.
When the first and second communications devices UE1, UE2 involved in the ProSe Communication are served by the same base station, e.g. the base station eNB1 as illustrated in FIG. 6, and network coverage is available, the system, e.g. a core network node or a base station, may decide to perform ProSe Communication using control information exchanged between the respective communications device UE1, UE2, the serving base station, e.g. the base station eNB1, and the core network, e.g. an Evolved Packet Core (EPC), as shown by the solid arrows in FIG. 6. For example, the control information exchanged may relate to session management, authorization, and/or security. For charging, signalling modifications should be minimized with respect to the existing architecture. The communications devices UE1, UE2 may in addition exchange control signalling via the ProSe Communication path as shown by the dashed arrow in FIG. 6.
FIG. 7 schematically illustrates an example control path for network-supported ProSe communication for the first and second communications devices UE1, UE2 when being served by different base stations, e.g. by the first base station eNB1 and the second base station eNB2, respectively.
When the first and second communication devices UE1, UE2 involved in the ProSe communication are served by different base stations, e.g. by the first and second base stations eNB1, eNB2, respectively, and when network coverage is available, the system, e.g. the core network node or the base station, may decide to perform the ProSe Communication using control information exchanged between the respective communications device UE1, UE2, the respective base station eNB1, eNB2, and the core network, e.g. the EPC, as shown by the solid arrows in FIG. 7. In this configuration, the first and second base stations eNB1, eNB2 may coordinate with each other through the EPC or communicate directly for radio resource management as shown by the dashed arrow between the eNBs in FIG. 7. For charging, signalling modifications should be minimized with respect to the existing architecture. The first and second communication devices UE1, UE2 may in addition exchange control signalling via the ProSe Communication path as shown by the dashed arrow between the first communications device UE1 and the second communications device UE2 in FIG. 7.
If network coverage is available to a subset of the communications devices comprised in the communications network, one or more Public Safety communications devices may relay radio resource management control information for communications devices that do not have network coverage. By the expressions “Public Safety communications device” and “Public Safety UE” when used in this disclosure is meant a communications device, e.g. a UE, that the Home Public Land Mobile Network (HPLMN) has configured to be authorized for Public Safety use, and which is ProSe-enabled and supports ProSe procedures and capabilities specific to Public Safety. The UE may, but need not, have a Universal Subscriber Identity Module (USIM) with one of the special access classes {12, 13, 14}. Further, the expressions “Public Safety communications device” and “Public Safety UE” are used interchangeably in this disclosure.
FIG. 8 schematically illustrates an example control path for Public Safety ProSe communication for the first and second communications devices UE1, UE2 without network support, e.g. without support from the communications network.
When network coverage is not available, the control path may exist directly between Public Safety UEs, e.g. between the first communications device UE1 and the second communications device UE2 when they are public safety UEs, as shown with the solid arrow in FIG. 8. In this configuration, the Public Safety UEs may rely on pre-configured radio resources to establish and maintain the ProSe Communication. Alternatively, a Public Safety Radio Resource Management Function, e.g. a Public Safety Radio Resource Controller, which may reside in another Public Safety UE, e.g. a third communications device UE3, may manage the allocation of radio resources for Public Safety ProSe Communication between the first and second communications devices UE1, UE2 as shown with the dashed arrows in FIG. 8.
LTE ProSe Discovery
A ProSe discovery process identifies that a first ProSe-enabled communications device is in proximity of a second ProSe-enabled communications device. By the expression “ProSe-enabled communications device” when used in this disclosure is meant a communications device enabled for ProSe communication, e.g. a communications device capable of ProSe communication. The ProSe discovery process uses an Evolved Universal Terrestrial Radio Access (E-UTRA), e.g. with or without an E-UTRA Network (E-UTRAN), or the EPC and comprises two discovery models. The first model is referred to as Model A and involves one communications device announcing “I am here” and the second model referred to as Model B involves one communications device asking “who is there” and/or “are you there”, see 3GPP TS 23.303 V13.0.0.
The LTE ProSe versus the IEEE NAN
While the IEEE NAN is targeting the use cases of social gaming, music sharing, group chatting, friend finder, home appliances control etc. promising affordable access to lots of different types of communications devices, the LTE ProSe is designed with the requirements of public safety and commercial consumer applications in mind and evolving toward a wider range of applications such as vehicle-to-infrastructure (V2X) communications, e.g., Vehicle-to-Vehicle (V2V) communications (see RP-151109 Feasibility Study on LTE-based V2X Services) or other latency- and reliability-demanding applications. Differences in the technologies and the targeted applications may mean that the IEEE NAN and the LTE ProSe may be preferable for different type of communication needs even if it is a part of the same commercial application.
Enabling or disabling the LTE ProSe may be subject to the user and/or operator preferences (ETSI TS 122.278 Section 7A.1). Similarly, the IEEE NAN is also expected to be either enabled or disabled by the user similarly to its predecessor Wi-Fi Direct, which is already deployed, as a part of mobile handsets and other portable devices. User preference on selecting the IEEE NAN and/or the LTE ProSe may be based on associated monetary cost, power consumed by the respective radio links, user perception and/or user choice about preferred radio technologies, etc. This means that even if the communications devices support both technologies, these technologies may not always be active simultaneously.
Mobile handsets supporting the IEEE NAN Release 1 are expected to be out in the market by end of 2015. The LTE ProSe functionality will be offered by the network operator and it is expected that the first release will include the support of the ProSe services within the network operator and not across operators, which will limit the number of services that may be offered by the LTE ProSe, as compared to services that may be offered by the NAN across operators.
Also, it is expected that, the NAN services being offered using unlicensed spectrum will continue to be free of cost. On the contrary, the LTE ProSe, at least for the initial phase, is expected to use licensed spectrum of the operator network. In this case, users need to pay for the ProSe. This may result in more services that are being offered within the NAN, as compared to the number of services being offered by the LTE ProSe.
Furthermore, the NAN based D2D communication is limited by lesser mobility, and by the dependence on the link quality in the unlicensed spectrum. On the contrary, the LTE based ProSe offers wider and more reliable access to the proximity service, mobility within and across cells and communication in the licensed spectrum, yet, as mentioned, still with some cost and constraints due to the potential operator involvement.
Research into discovering the neighbour devices is currently being conducted within the single radio access technology e.g. within the Wi-Fi and within the 3GPP.
The IEEE Pre-Association Discovery Procedures
One of the amendments to the IEEE 802.11 standard defines a pre-association discovery protocol that may be used between the communications device, e.g. a wireless station (STA), and an Access Point (AP) for service advertisement and service discovery. The standardization is on-going within the IEEE 802.11 Task Group aq (TGaq). The TGaq has specified a mechanism by which the STA and the AP may advertise and discover services in a pre-association state without the need to carry lengthy association and authentication procedures, which results in low latency for the discovery of the service. FIG. 9 schematically illustrates frame exchange for the pre-association service discovery procedure.
The AP advertises, in Action 901, a Service Hash element in one or more Beacon frames that it sends out periodically. The Service Hash element carries hashed information on all the services that are supported by a Basic Service Set (BSS) served by the AP. When a communications device, e.g. a STA, reads the Service Hash element, it tests, in Action 902, whether the service it is interested in is present in the hash by for example using a Bloom filter mechanism of testing for a false positive match. The Bloom Filter provides a probabilistic representation of an available set of services in the BSS or in an external network reachable via the BSS. If the communications device, e.g. the STA, determines that the probability of the service being present in the hash is rather large, the STA queries, in Action 903, further information from the AP via a Probe Request frame, indicating the particular service, e.g. a service named Y as indicated in FIG. 9, that is being queried for. The AP then provides, in Action 904, additional information, e.g. in a Probe Response, on that particular service. In response to the received additional information, the STA transmits, in Action 905, to the AP, a Pre Association Discovery (PAD) Service Information (SI) Request comprising the service name Y and an SI Query Request. The PAD is a discovery service provided to allow non-AP STAs, in a pre-association state, to discover information concerning services that are offered by a Primary BSS (PBSS), a BSS or an external network. This information may allow a STA to choose during network selection, which PBSS or BSS, e.g. which communications network, to associate with to obtain services. The AP may transmit, in Action 906, to the STA, a PAD Service Information Response comprising the service name Y and a SI Query Response. Thereafter, in Action 907, an association procedure is accomplished between the STA and the AP.
A drawback with the prior art is that when two or more RATs are available it may be difficult for a communications device to decide which RAT is the best RAT to use.
A further drawback with the prior art IEEE 802.11 NAN and 3GPP LTE ProSe technologies is that they are specified by different standardization bodies with major differences in terms of targeted use cases and services, as well as in terms of technical aspects, which may affect the user experience.